With the continuous development of LCD (Liquid Crystal Display) display technologies, people have continuously increasing demands on the quality of the LCD. An IPS (In-Plane Switching) type LCD with a higher contrast and wider visible view angle has been more and more popular with people.
Being different from a TN (Twisted Nematic) type liquid crystal display, the liquid crystal of the IPS type liquid crystal display is applied with a horizontal electric field, and then the liquid crystal molecules can conduct twisted movement within a plane parallel to a substrate. The twisting of the liquid crystal molecules will change the travelling direction of light. In order to increase the contrast of the liquid crystal display, the current IPS type liquid crystal display needs to dispose equivalent polarizers at two sides of a liquid crystal panel. The structure of the IPS type liquid crystal display in the prior art is shown in FIG. 1, and the liquid crystal display comprises an upper optical compensation structure 11 having a polarizing function, a liquid crystal panel 12 and a lower optical compensation structure 13 arranged opposite to the upper optical compensation structure 11. The upper optical compensation structure 11 further comprises a first TAC layer 111 and a second TAC layer 113 having a polarizing effect and an optical compensation function, and a first PVA layer 112 as a polarizing film layer which is located between the first TAC layer 111 and the second TAC layer 113, a third TAC layer 131, a second PVA layer 132 and a fourth TAC layer 133 contained in the lower optical compensation structure 13 correspond to the second TAC layer 113, the first PVA layer 112 and the first TAC layer 111 of the upper optical compensation structure 11, respectively, and the hierarchical structure relationship among the respective layers is shown in FIG. 1. The IPS type liquid crystal display with this structure has a disadvantage that color shift may occur in the diagonal direction of the liquid crystal panel. Taking the IPS type liquid crystal display shown in FIG. 1 as an example, the Δnd of the current liquid crystal panel 12 is usually 392.7 nm, the horizontal phase differences Re of the second TAC layer 113 and the third TAC layer 131 are both 3 nm, and their thickness direction phase differences Rth are both 40 nm, and thus generated color shift in the diagonal direction is shown in FIG. 2. The prior art cannot solve the problem of color shift generated in the diagonal direction of the liquid crystal panel.